Results 11 to 20 of about 507,111 (281)
Journal of Graph Theory, 2023 AbstractGiven a finite simple graph , an odd cover of is a collection of complete bipartite graphs, or bicliques, in which each edge of appears in an odd number of bicliques, and each nonedge of appears in an even number of bicliques. We denote the minimum cardinality of an odd cover of by and prove that is bounded below by half of the rank over
Calum Buchanan +6 more
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Arborescences of covering graphs
Algebraic Combinatorics, 2022 An arborescence of a directed graph Γ is a spanning tree directed toward a particular vertex v. The arborescences of a graph rooted at a particular vertex may be encoded as a polynomial A v (Γ) representing the sum of the weights of all such arborescences.
Chepuri, Sunita +5 more
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, 2008 We study problems that arise in the context of covering certain geometric objects called seeds (e.g., points or disks) by a set of other geometric objects called cover (e.g., a set of disks or homothetic triangles). We insist that the interiors of the seeds and the cover elements are pairwise disjoint, respectively, but they can touch.
Atienza, Nieves +13 more
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Discussiones Mathematicae Graph Theory, 2023 The $k$-token graph $T_k(G)$ is the graph whose vertices are the $k$-subsets of vertices of a graph $G$, with two vertices of $T_k(G)$ adjacent if their symmetric difference is an edge of $G$. We explore when $T_k(G)$ is a well-covered graph, that is, when all of its maximal independent sets have the same cardinality.
F.M. Abdelmalek +3 more
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Ramanujan coverings of graphs [PDF]
Proceedings of the forty-eighth annual ACM symposium on Theory of Computing, 2016 Let $G$ be a finite connected graph, and let $ $ be the spectral radius of its universal cover. For example, if $G$ is $k$-regular then $ =2\sqrt{k-1}$. We show that for every $r$, there is an $r$-covering (a.k.a. an $r$-lift) of $G$ where all the new eigenvalues are bounded from above by $ $.
Hall, Chris +2 more
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Journal of Combinatorial Theory, Series B, 1997 A covering projection from a graph \(G\) onto a graph \(H\) is a ``local isomorphism'': a mapping from the vertex set of \(G\) onto the vertex set of \(H\) such that, for every \(v\in V(G)\), the neighborhood of \(v\) is mapped bijectively onto the neighborhood (in \(H\)) of the image of \(v\).
Kratochvı́l, Jan +2 more
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Minimal Normal Graph Covers [PDF]
Combinatorica, 2017 A graph is normal if it admits a clique cover $\mathcal C$ and a stable set cover $\mathcal S$ such that each clique in $\mathcal C$ and each stable set in $\mathcal S$ have a vertex in common. The pair $(\mathcal{C,S})$ is a normal cover of the graph. We present the following extremal property of normal covers.
Gajser, David, Mohar, Bojan
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PELABELAN SELIMUT TOTAL SUPER (a,d)-H ANTIMAGIC PADA GRAPH LOBSTER BERATURAN L_n (q,r)
E-Jurnal Matematika, 2017 Graph labelling is a function that maps graph elements to positive integers. A covering of graph is family subgraph from , for with integer k. Graph admits covering if for every subgraph is isomorphic to a graph .
TIRA CATUR ROSALIA +2 more
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Homotopy Covers of Graphs and Lifting Property
Wasit Journal for Pure Sciences, 2023 The aim of this paper We create requirements for a graph cover to have the homotopy lifting property of topological space covers, or A-Homotopy lifting property.
salwan abdlwahab, Daher W. Al Baydli
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Graph homomorphisms and components of quotient graphs [PDF]
, 2016 We study how the number $c(X)$ of components of a graph $X$ can be expressed through the number and properties of the components of a quotient graph $X/\sim.$ We partially rely on classic qualifications of graph homomorphisms such as locally constrained ...
Bubboloni, Daniela
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